Chusetts



SUNITED STATES PATENT- OFFICE.

AARON H. PARKER AND ARTHUR H. 'STODDARD, OF BOSTON, MASSA- CHUSETTS.

METHOD OF PREPARING PORCELAIN TEETH.

SPECIFICATION forming part of Letters Patent No. 418,380, dated December31, 1889.

Application filed May 13, 1889. Serial No. 810,632. (No specimens.)

To all whom it may concern.-

'Be it known that we, AARON H. PARKER and ARTHUR H. STODDARD, of Boston,in the county of Suffolk and State of Massachusetts, citizens of theUnited States, have invented certain new and Improved Methods ofPreparing Porcelain Teeth, of which the following is a specification.

Our invention relates to the art or method of preparing artificial teethcomposed of a body of mineral earth with an outside coating ofvitrifiable material or glaze, the whole being combined with suitablemetallic oxides to give the desired color for the various portions ofthe finished work when the operation of baking is completed.

The object of our invention is to furnish an improvement in the methodof accomplishing this result, whereby a gain in time and fuel expendedis obtained, together with the certainty of a successful result of thebaking, and other advantages hereinafter set forth.

It has long been known that the materials of which artificial teeth arecomposed could be baked by placing them within a closed chamber ormuffle of fire-clay or analogous material, and then subjecting thismuffle within a suitable furnace to the action of a high temperatureprolonged for a considerable length of time. This method has also withinthe last ten years been improved by the use as a fuel or combustionmaterial of mingled fuel-gas and atmospheric air, supplied underpressure to the combustion-chamber of the furnace and around the mufflein which the teeth to be baked are placed. It has been found, however,that whether with the old fuelsuch as coal or coke-01 with thatfurnished by the mingled gas and air, there was a liability todiscoloration in the finished teeth, whereby, instead of the propercolor being obtained, a different and objectionable color resulted, dueto the operation commonly known as gasing. It has been believed thatthis gasing was the result of chemical action, a portion of the oxygeninthe metallic oxide employed to give the color having been withdrawnduring the baking process by chemical union with substances contained inthe vapors in the interior of the muffle. Since the introduction of thegas and air as a fuel, and within a comparatively recent period, it hasbeen proposed to obviate this gasing by providing a constant supply ofair to the interior of the muffle during the baking, of atmospheric airfrom without, the theorybeing, first, that the air thus introduced intothe lnufile would supply any oxygen which might otherwise have beengiven up by the oxide forming the coloring material of the teeth; and,secondly, that the introduction of pure air into the muffle wouldpreclude the entrance therein of products of combustion of the gas andair, and thereby lessen in this way the tendency to gasing. Under allmethods, however, which to our knowledge have heretofore been employedfor baking porcelain teeth a inuffle has uniformly and invariably beenused, and it has heretofore been believed that the use of such a mufflewas essential, and, furthermore, that it was essential that the productsof combustion of the fuel employed should, through the instrumentalityof the muffle, be out off from coming into contact with the porcelainduring the process of baking. The muffle, although hitherto universallyused, has been generally recognized as objectionable, in that itnecessitates an increased area of the heating-chamber and a consequentincreased loss of heat by radiation and a greater consumption of fuel,while the difficulty of prepari the mufile and of keeping it free fromcracks has been material. Furthermore, while the work is shut up in themuffle it cannot be seen. It has therefore been necessary heretofore,whenever it was desired to examine the work, to open the door of thefurnace and muffle, thereby lessening the temperature within-the muffleand otherwise causing inconvenience to the operator.

According to our present improvement we dispense entirely with anymuffle or other barrier between the work and the combustion medium, andcause the products of the combustion of gas combined with atmosphericair under pressure to pass directly over and upon the porcelain to bebaked.

The discovery underlying our invention we believe to be this-viz., thata sufficient amount of air may be mingled With the gas to form whenignited a fuel capable of producing the intense heat necessary for rapidand successful baking, While at the same time i the oxygen in themetallic oxide forming the coloring-matter of the teeth to be chemicallyreleased, and thereby to prevent discoloration by gasing, so called.

In carrying out our improved method of preparing teeth we first form thematerial to compose the body. For this purpose We take silex andfeldspar, both in powdered form, and unite them into a plastic mass bythe addition of fine clay. The proportions of the ingredients may bevaried. considerably; but We have found in practice that for a batch ofsixty-four teeth three drams of silex and four drams of feldspar may bemixed with one pennyweight of clay. In order to give the finishedproduct the slightly-yellowish tint necessaryto imitate nature, we add apenny- Weight of oxide of titanium. As the titanium forms the coloringmaterial, it is obvious thatin a particular case Where a greater or lessamount of color is required the proportion of titanium should be variedaccordingly. The mixture above described is then dried slightly, molded,and carved to represent or produce the forms of teeth required. Theenamel-paste is a then applied, this consisting of powdered feldspar forthe glaze and suitable metallic oxides to give the desired color. Togive the red color of the gum, we prefer to use oxide of gold, andplatinum-sponge may be employed to give a bluish-gray tint to otherparts of the teeth. The work is now ready to be placed in the furnace,which is accordingly done, an open platinum dish being used as areceptacle for the Work, which is thus submitted to the direct access ofthe products of combustion of the mixed gas and air. These, supplying tothe teeth a sufficiency of oxygen, neutralize any tendency of the oxygenin the metallic oxide to be released, as above stated, and thus thediscoloration by gasing is prevented.

We claim The improved art, method, or process of preparing porcelainteeth, which consists in mixing with the mineral earth base, metallicoxides to give coloring-matter, and then submitting the Whole to thedirect contact of the products of combustion of a mixture of aninflammable gas and atmospheric air, as set forth.

In testimony whereof We have hereunto subscribed our names this 11th dayof May, A. D. 1889.

AARON H. PARKER. ARTHUR H. STODDARD. \Vitnesses:

ELLEN B. TOMLINSON, J OHN H. TAYLOR.

